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Car: Mercedes-Benz | CLK | W209 | Avantgarde | Coupe
Engine: CDi | 2.7 | Inline 5 | (170 BHP) | Turbocharged | Diesel

CLK Lowering springs

I recommend choosing a quality brand for all suspension components, cheaper brands are often poorly developed and in my experience the spring rates are too high for comfortable road use. Quality manufacturers will invest money in R&D to get the best comfort/performance balance for the road, and will often list different part numbers to suit the weight of particular engines and specifications.

I chose Koni part number 1020-6078 for my CLK, which is a spring pack offering an all-round 35mm drop.

Front

Strut removal

w209springs

The front suspension on the C/CLK is extremely easy to remove. With the wheel removed and car jacked up, the strut is removed as follows:

w209springs

The strut is now free to be withdrawn. The photo left shows my front strut and standard spring next to the uncompressed lowering spring. Now, typically with a lowering spring the uninstalled height is somewhere close the standard springs installed height thus making installation a cinch. The CLK is different and is the first car I've worked on that uses a very high spring length/damper piston length ratio.

This configuration serves to put the installed spring under very high compression, even with a shortened spring. I do not yet understand the effect of this compared with a more traditional lower spring length/damper length ratio; I assume the static compression is paired with a softer spring rate to change suspension dynamics in order to lessen NVH and/or provide a more comfortable ride. If anyone reading this article can provide more info, please leave a comment as I'd be interested to learn more.

Spring removal

As mentioned in the previous section, the C/CLK front springs are installed under an incredible amount of compression and care should be taken when removing them, in fact, I recommended taking the uninstalled strut/spring to a garage and have them install the new springs. 'Claw' type DIY spring compressors should not be used with the front suspension, a professional tool must be used.

In the end, I decided to stick with the standard front springs as they were firm and low enough for a daily driver.

information

Info

CLK Lowering springs

A special tool is required to remove the front strut spring cup securing nut, which itself must be removed to allow the spring to uncompress on the strut before it can be withdrawn.

The special tool (right – internet photo) is available direct from Mercedes-Benz, the part number is: 203-589-00-07-00 Strut Retainer Tool. The price is around £25 at the time of writing.

Rear

w209springs

Rear spring replacement is relatively simple and the springs themselves are under what I'd term a 'standard' amount of compression, because of this the uncompressed spring length gives a much better indication of lowering distance.

The photo to the right shows a Koni spring next to my standard Avantgarde spring; a height difference of approximately 35mm can be observed, which is the stated lowering measurement.

w209springs

With the rear of the car on axle stands, remove the plastic guard on the bottom suspension arm, then remove the strut securing nut and bolt completely and loosen the outside arm mounting nut, leaving the bolt in place so that the arm can pivot around it.

Now place a jack underneath the arm and raise it so it touches the bottom of the arm.

w209springs

Next, ensure that the jack is secure and remove the inside lower arm mount nut & bolt, and lower the jack, which will bring down the arm and uncompress the spring as it goes. (No need to remove the entire arm as I did - right)

The old spring can now be removed entirely and the new one put back in it's place, also the damper if required; the top mount bolt is inside the boot. It is recommended that new nuts and washers are used on the lower arm inside bolts.

The refit procedure is the exact opposite of removal, this time using the jack to raise the arm and compress the spring.

© Mark Stewart, Saturday 18th October 2008
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